Ultrathin dual-layer triple-band flexible microwave metamaterial absorber for energy harvesting applications

Abstract

An ultrathin dual-layer flexible metamaterial absorber with triple-band for RF energy harvesting applications has been reported in this article. The sub-wavelength unit cell of the proposed absorber is composed of six distinct concentric annular having outer circumference of ring and octagonal inner circumference. The metallic resonators are constructed from copper foil self-adhesive tape which are affixed on flexible neoprene rubber sheet terminated by metal ground plate. The proposed absorber prototype is ultrathin and compact with the thickness less than 0.037λ 0 and cell size less than 0.2λ 0 at the lower absorption frequency of 1.75 GHz. Flexible dual-layer absorber exhibits triple absorption peaks of 96.91%, 96.41% and 90.12% at 1.75 GHz, 2.17 GHz and 2.6 GHz with full width at half maximum (FWHM) bandwidth of about~6.5%. The RF performance of proposed absorber is numerically computed for different polarization and incidence angle variations. The absorption value is above 76% for the oblique incidence angle up to 45 in TE mode operation, whereas the absorption value is 94% for oblique incidence angle up to 60 in TM mode operation. The measured outcomes are in agreement with the numerically calculated results. The energy harvesting potential of the proposed absorber structure is numerically confirmed by the resulting improved RF absorption value in dependence to different resistive loading of the polarization insensitive unit cells. K E Y W O R D S energy harvesting, metamaterial, metamaterial absorber

Flexible Antennas: A Review

“…Most common elastomeric materials have low dielectric constants. This low value can be increased by mixing the substrate with high dielectric constant materials such as ceramics like Ba x Sr 1−x TiO 3 [ 258 ] , BaTiO 3 [ 257 ], NdTiO 3 [ 259 ], MgCaTiO 2 [ 259 ], CNTs [ 260 ], and nanoparticles [ 261 ]. Metamaterial based flexible antenna is a relatively new development and has found its way in the commercial market because of its characteristics like lightweight, robustness, and reconfigurability [ 239 , 262 , 263 , 264 , 265 ].…”

An Ultrathin Compact Polarization-Sensitive Triple-band Microwave Metamaterial Absorber

“…The novel structure on the top layer of the MMA consists of two modified metallic square-shaped resonators to exhibit perfect absorption at all resonating frequencies. Each resonating element in the unit cell has its own absorptivity and resonant frequency; 15,20,21 however, coupling between two metallic resonators of the proposed MMA creates an extra absorption peak utilizing the optimized geometrical structure and its dimensions. 22 The optimized parameters of the MMA are a = 10, b = 6.75, c = 5.565, d = 2.92, e = 1.75, f = 0.94, g = 1.58, i = 0.4 and j = 0.3 mm.…”

“…6 These structures have the ability to minimize the reflection by matching the impedance of the MMA to free space, and the transmission is eliminated by the ground plane to achieve perfect absorption. 8 Till now, various metamaterial-based structures have been investigated, including split-ring structures, 11 ring-shaped, 14,15 square-shaped, 10,16 cutwire 17 and spilt-Jerusalem cross-resonators 18 to demonstrate their performance with dual-, 11,14,17,19 triple-, 15,17,20 multi- 16,18 and broadband 10 operations. To achieve multi-band absorption performance, several efforts have been carried out using orthogonal arrangements of different metallic resonators 10,17 or multilayered metallic structures separated by dielectric substrates.…”

“…To achieve multi-band absorption performance, several efforts have been carried out using orthogonal arrangements of different metallic resonators 10,17 or multilayered metallic structures separated by dielectric substrates. 16,20,21 Recently, a single-layer triple-band absorber was proposed utilizing three concentric closed circular ring resonators in a unit cell. 15 However, these approaches may suffer from technical difficulties, like fabrication complexity, which significantly affect their utilization for practical applications.…”

“…The obtained results suggest the proposed MMA exhibits a higher absorption rate than that of the previously reported triple-band absorbers. 9,15,20,21…”